There are a number of topographical, anatomical, and site-specific differences between human skin on the sole and the palm (also called palmoplantar skin or palmoplantaris) and on the trunk (also called non-palmoplantar skin or non-palmoplantaris) in terms of thickness and pigmentation. Not only is palmoplantar skin much thicker and less hairy than is skin in other regions of the body, but melanocytes in those areas are less dense and produce significantly less melanin pigment than non-palmoplantar skin.
Many dermatological conditions would be improved by an increase in skin thickness, a decrease in skin pigmentation, or a decrease in hair growth. For instance, skin thickening would be desirable in a subject that has a skin graft, a skin ulcer, a skin abrasion or avulsion/excision (such as one that leaves a volume defect), an injury or predisposition to injury caused by a repetitive impact or mechanical stress, age-related skin changes (for instance, thinning or wrinkled skin), or skin damage due to steroid treatment. A decrease in skin pigmentation would be helpful when the subject has a condition such as uneven skin pigmentation, hyperpigmentation, post-inflammatory pigmentation, ephelides, fragrance dermatitis, sun-damaged skin, a pigmented birthmark, lentigos, lichen simplex chronicus, melasma, porphyria cutanea tarda, Addison's disease, Peutz-Jeghers syndrome, acanthosis nigricans, or when depigmentation is desired in a subject with widespread vitiligo. Decreased hair growth may be cosmetically desirable on an upper or lower extremity or axillary skin, or when a subject has, for instance, hirsutism, congenital adrenal hyperplasia, polycystic ovarian syndrome, hypertrichosis, porphyria cutanea tarda, or increased vellus hair due to anorexia nervosa.
Given the foregoing, it would be desirable to have methods or compositions that could induce non-palmoplantar skin to adopt one or more of the characteristics of palmoplantar skin.